Nissan probes into electron activity to prolong battery life

A joint R&D effort between the Nissan Motor Company subsidiary, Nissan Arc Ltd., and several academic institutions bore an analysis method that facilitates an improved understanding of the electron activity in the cathode material of lithium ion batteries during charging and discharging.

The observation and monitoring of the active materials within electrodes is said to be a key step to boosting battery performance of electric vehicles. Nissan believes that applying the analysis technique to future research and design of battery materials could enable high-capacity and high-durability batteries developed that may extend the driving distance of zero emission EVs and improve their durability.

Together with Tokyo University, Kyoto University and Osaka Prefecture University, Nissan Arc devised the analysis method by combining x-ray absorption spectroscopy that utilises L-absorption edges and the first principle calculation from Japan's Earth Simulator supercomputer.

To develop high-capacity, long-life lithium ion batteries, the maximum amount of lithium needs to be stored in the electrode's active material, which allows it to generate the highest possible number of electrons. To develop such a material, an accurate reading of the electron activity inside the battery is vital. The analysis method allows engineers to identify where electrons are being emitted from the active materials (manganese, cobalt, nickel and oxygen) in electrodes. The technique also can see how many electrons are emitted.

X-ray absorption spectroscopy had been used in the past to analyse batteries. However, the majority of this analysis was done using K-absorption edges that can only observe restrained electrons in the atom (electrons that are not involved in the charging and discharging due to the vicinity to the nucleus) and not the actual electrons involved in cell reaction. By applying x-ray absorption spectroscopy that utilises L-absorption edges, electrons that were directly involved with the cell reaction can be observed.

Nissan Arc has used the new analysis technique to investigate lithium-rich high-capacity electrode materials which are considered promising agents to increase energy density by 50 per cent. The analysis revealed that at a high potential state, electrons originating from oxygen were active during charging.

Electrons that originated from manganese were observed to be active during the discharge reaction.